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Tropical sea surface temperatures following the middle Miocene climate transition from laser-ablation ICP-MS analysis of glassy foraminifera

Nairn, Michael G., Lear, Caroline H., Sosdian, Sindia M., Bailey, Trevor R. and Beavington-Penney, Simon 2021. Tropical sea surface temperatures following the middle Miocene climate transition from laser-ablation ICP-MS analysis of glassy foraminifera. Paleoceanography and Paleoclimatology 36 (3) , e2020PA004165. 10.1029/2020PA004165

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Abstract

The unipolar icehouse world of the mid-late Miocene is a poorly understood interval in the evolution of Cenozoic climate, and the sparse proxy-based climate reconstructions are associated with large uncertainties. In particular, tropical sea surface temperature (SST) estimates largely rely on the unsaturated alkenone U proxy, which fails to record temperatures higher than 29˚C, and Mg/Ca ratios of poorly preserved foraminifera. We reconstruct robust, absolute, SSTs between 13.5 Ma and 9.5 Ma from the South West Indian Ocean (paleolatitude ~5.5˚S) using Laser-Ablation (LA-) ICP-MS microanalysis of glassy planktic foraminiferal Mg/Ca. Employing this microanalytical technique, and stringent screening criteria, permits the reconstruction of robust paleotemperatures from Mg/Ca thermometry using foraminifera which although glassy, are contaminated by authigenic coatings. Our absolute estimates of 24-31⁰C suggest that SST in the tropical Indian Ocean was relatively constant between 13.5 and 9.5 Ma, similar to those reconstructed from the tropics using the U alkenone proxy. This suggests an interval of enhanced polar amplification between 10 and 7.5 Ma, immediately prior to the global late Miocene Cooling. The mid-to-late Miocene is proposed as a key interval in the transition of the Earth’s climate state towards that of the modern-day.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Additional Information: This is an open access article under the terms of the Creative Commons Attribution License
Publisher: American Geophysical Union
ISSN: 2572-4525
Funders: NERC
Date of First Compliant Deposit: 3 February 2021
Date of Acceptance: 1 February 2021
Last Modified: 06 May 2021 13:07
URI: http://orca.cardiff.ac.uk/id/eprint/138227

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